'Cosby Show' enthusiasts will immediately pick up on the reference from the series' second season where in episode 19 (entitled Full House and aired in February 1986) Cliff Huxtable (Bill Cosby) walked in on his daughter Denise (Lisa Bonet) and her new suitor Eddie Lakehart grooving to Black Uhuru's "Sponji Reggae"; specifically Denise and Eddie's repetitive "Hey Mon" adlibs.
While Cosby did not catch that reference right away, he did have a blast dancing along to the song, strutting up and down stairs and getting face-to-face with vocalist Black Thought, who did an impressive job singing the tune, accent and all. Fallon certainly tried to keep up too.
With his comedic timing still ticking, Cosby then proceeded to show Fallon how to walk the curb to the sound of Reggae and how the groove is reminiscent of walking with a limp.
See him dance to Sponji Reggae